Air compressor and method of operation

ABSTRACT

An air compressor (10) includes an air pump (34) with a pump inlet (34a) for receiving air to be pressurized and a pump outlet (34b). An air tank (14) includes a tank inlet (14a) coupled with the pump outlet (34b) for receiving pressurized air from the air pump (34), and a tank outlet (14b) for directing pressurized air from a tank outlet (14b) to at least one pneumatic device (24). A brushless DC motor (36) includes a rotatable output (36a) coupled with the air pump (34) for operating the air pump (34) to pressurize air. A control (42) is electrically coupled to the brushless DC motor (36). The control (42) changes the level of electric current drawn by the brushless DC motor (36) to thereby change the rate of rotation of the rotatable output (36a) and/or the pump performance level.

CROSS-REFERENCE TO RELATED APPLICATION

The application claims priority to U.S. Provisional Application Ser. No. 62/378,196, filed Aug. 22, 2016 (pending), the disclosure of which is hereby incorporated by reference herein.

TECHNICAL FIELD

The invention generally relates to air compressors and, more particularly to control components and methods of operating air compressors such as those used for home improvement purposes.

BACKGROUND

Air compressors are used in various situations to provide compressed or pressurized air. These situations may, for example, include using air compressors at work sites such as home or other building construction jobs, to operate pneumatic equipment and tools. Often, the electrical power delivered to an electrically operated air compressor is substandard. This may be the result of the electrical connection between a main power line and the job site and/or because of using lengthy electrical extension cords between a power connection and the electrically operated air compressor. As a result of substandard power or voltage supplied to the air compressor, operational difficulties can be encountered. One of these is during start up of the air compressor. Because of high physical resistance created by pistons in the air pump initially moving to compress air in a piston chamber, the electric motor used to move the pistons can experience very high initial loading. Substandard voltage input can be insufficient to turn the motor output shaft during these high initial load conditions and, likewise, fail to move the pistons of the air pump through a full initial cycle.

Air compressors can also present undesirable noise during operation. While noise is not a significant factor at many job sites, other sites such as residential construction or home improvement locations demand lower noise in many instances.

Finally, various electric air compressors are run on AC power, such as supplied by a standard 110/120V wall outlet, while others are powered by a DC power supply, such as a battery. Those that are run on a battery typically are for smaller projects demanding less performance or for running a single pneumatic tool operated by a single user as opposed to multiple tools coupled to the same air compressor.

It would be desirable to provide an electrically operated air compressor and method of use to address these and other concerns and issues in the industry.

SUMMARY

Generally, an illustrative embodiment the invention provides an air compressor comprising an air pump including a pump inlet for receiving air to be pressurized and a pump outlet. The air compressor further comprises an air tank including a tank inlet coupled with the pump outlet for receiving pressurized air from the air pump, a tank outlet for directing pressurized air from the tank to at least one pneumatic device. The air compressor further comprises a brushless DC motor including a rotatable output coupled with the air pump for operating the air pump to pressurize air. In accordance with one exemplary inventive aspect, a control is electrically coupled to the brushless DC motor. The control changes the level of electric current drawn by the brushless DC motor between at least a first level and a second, different level to thereby change the rate of rotation of the rotatable output and/or the pump performance level. The control, in this regard, changes the electric power or current profile of the motor in response to either an automated, programmed routine or a manual input by a user.

An electric power supply may be coupled to the brushless DC motor and to the control. The electric power supply may further comprise a DC power supply, such as a battery, or an AC power supply coupled to an AC/DC converter. The control may detect the DC power supply or battery as the electric power supply and, in response, cause a predetermined level of electric current to be drawn by the brushless DC motor from the DC power supply or battery. The control may further comprise an adjustment device operable by a user to change the level of electric current drawn by the brushless DC motor to thereby change the rate of rotation of the rotatable output and/or the air pump performance level. The adjustment device may be operable to allow the user to select between an AC power supply and a DC power supply, such as a battery. Optionally, the adjustment device may be used as a sound control adjustment. For example, this may lower the pump performance level and thereby lower the noise or sound level emitted by the pump. The control may further include a mode, wherein upon activation of the brushless DC motor, the control gradually increases the level of electric current drawn by the brushless DC motor to thereby gradually increase the rate of rotation of the rotatable output and/or gradually increase the air pump performance level. The control increases the level of electric current drawn by the brushless DC motor to a level corresponding to an operating performance level of the air pump.

The invention further provides a method of operating an air compressor generally as described herein. The method comprises supplying electric current to the brushless DC motor to rotate an output of the brushless DC motor; operating the air pump with the rotatable output of the brushless DC motor; directing pressurized air into the tank from the air pump; and changing the level of electric current drawn by the brushless DC motor using an adjustable electric current control coupled to the brushless DC motor to thereby change the rate of rotation of the rotatable output and/or the pump performance level.

The electric current may be supplied from an AC power supply or from a DC power supply. In the case of an AC power supply, there would be a conversion from AC power to DC power. An exemplary DC power supply would be a battery. The method may further comprise detecting a battery as the electric power supply and adjusting the level of electric current drawn by the brushless DC motor to a predetermined level of electric current. Changing the level of electric current drawn by the brushless DC motor may further comprise using an adjustment device operable by a user. The adjustment device may be used to select between an AC power supply and a battery as an electric power supply coupled to the brushless DC motor. Supplying electric current to the brushless DC motor may further include initiating a control mode that gradually increases the level of electric current drawn by the brushless DC motor upon activation of the brushless DC motor to thereby gradually increase the rate of rotation of the rotatable output and/or gradually increase the air pump performance level. The level of electric current drawn by the brushless DC motor is then increased to a level corresponding to an operating performance level of the air pump.

Various additional objectives, advantages, and features of the invention will be appreciated from a review of the following detailed description of the illustrative embodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.

FIG. 1 is a perspective view of an illustrative air compressor in accordance with an embodiment of the invention.

FIG. 2 is a block diagram illustrating the air compressor of FIG. 1 in diagrammatic form.

DETAILED DESCRIPTION

Referring first to FIG. 1, an electrically operated air compressor 10 is shown and generally includes an electric motor and an air pump contained in a housing 12, and an air tank 14. A knob 16 is provided on a power control box 18 for turning the air compressor 10 on and off. The air compressor 10 further includes a control panel 20 that includes dials or gauges as needed. For example, one or more air pressure gauges 22 may be provided for displaying air pressure being delivered to one or more pneumatic device(s) 24 (FIG. 2). An air pressure regulating knob 26 is provided, as well as a hose connector 28 for the pneumatic device(s) 24. An electric cord set 30 extends from the air compressor 10 and may be plugged into a 120V AC receptacle (not shown). Alternatively, the power supply may be a DC power supply, such as a battery. In the case of using AC power, the power control box 18 includes an AC/DC converter.

Referring now more specifically to FIG. 2, the air compressor 10 of FIG. 1 is shown in block diagram form. In this regard, like reference numerals in FIG. 2 represent like structure or components shown in FIG. 1. Air 32 from the surrounding environment, for example, enters an air pump 34 through a pump inlet 34 a. The air pump 34 is operated by a brushless DC motor 36 which receives power from a suitable electric power supply 40. Specifically, the pump 34 is operated by a rotatable output 36 a of the motor 36. That power supply 40 may comprise a DC power supply, such as a battery which may be a lithium ion battery, or from an AC power supply such as a standard 120V outlet or receptacle. The brushless DC motor 36 is coupled to a suitable motor control 42, which may be a programmable microprocessor-based control such as a PC board, the function of which will be described in more detail below. The DC power may further be used to operate the control 42. The air pump 34 pressurizes the air received from the air inlet 34 a and directs the pressurized air through an air outlet 34 b into a tank inlet 14 a. In a known manner, the tank 14 is then used to supply pressurized air through a tank outlet 14 b either constantly or intermittently to one or more pneumatic devices 24. For example, in a home improvement type situation such as home construction or other building construction, the pneumatic devices 24 may be nail guns, paint sprayers and the like. As the air pressure in the tank 14 is depleted by use of such pneumatic devices 24, it must be replenished with additional pressurized air from time to time. Therefore, the air pump 34 is activated through the control-operated brushless DC motor 36 to recharge or re-pressurize the tank to a predetermined pressure level or range.

Generally, the control 42 is electrically coupled to the brushless DC motor 36 and the control 42 changes the level of electric current or amperage drawn by the brushless DC motor 36 to thereby change the rate of rotation of the rotatable motor output 36 a. Optionally, or additionally, the pump performance level is changed as well. This feature of the control 42 may be useful for various situations. For example, this feature may be used as a sound level control when the air pump 34 is pressurizing the tank 14. Normally, to pressurize the tank 14 as fast as possible, the air pump is run at high RPM, such as 2,000 RPM to 3,000 RPM. This creates a high level of noise which may be undesirable in various situations. To lower the sound level, the air pump 34 is run at lower RPM by use of the control 42 and, specifically, by use of an adjustment device such as a dial 50 on the front of the air compressor 10 (FIG. 1). Optionally, the sound reducing feature may be automatic. For example, the control 42 may reduce the pump performance level when a predetermined sound level is detected, or when a low sound level mode is selected by the user. For the manually operated embodiment, the user may rotate the dial 50 to adjust the performance and/or sound level of the air pump 34 between high and low settings or levels. At a lower performance level, the control 42 reduces the rate of rotation or operation of the air pump 34 thereby slowing the pressurization of the tank 14 but also reducing the noise or sound level associated with the air pump 34.

In another aspect, the control 42 can automatically detect that the power supply is a DC power supply 40 such as a battery and, in response, cause a predetermined lower level of electric current to be drawn by the brushless DC motor 36 from the battery. This predetermined level of electric current would be less than the level of current drawn, for example, when the power supply 40 is an AC power supply such as a standard 120V electrical outlet. Optionally, an adjustment device, such as a knob, switch or dial 52, may be provided on the control panel 20 of the air compressor 10 (FIG. 1), to allow the user to select between an AC power supply and a DC power supply, such as a battery. When the AC power supply is selected, the control 42 will allow the brushless DC motor 36 to draw a higher level of electric current than when the user selects a DC power supply.

In another aspect, the control 42 further includes a mode which may be initiated when the motor is started. Upon activation of the brushless DC motor 36, such as by pushing a start button or turning the start knob 16, the control 42 will send the appropriate signal or signals to gradually increase the level of electric current drawn by the brushless DC motor 36 and thereby gradually increase the rate of rotation of the rotatable output 36 a associated with the brushless DC motor 36. This gradually increases the air pump 34 performance level upon start-up. For example, instead of the air pump 34 immediately attempting to operate at a maximum of 2,000 RPM to 3,000 RPM when a start button or start knob 16 is activated by the user, the air pump 34 may be ramped up in a stepwise fashion for example from 200 RPM to 400 RPM to 600 RPM, etc., until the operating performance level is reached. Alternatively, the ramp-up in pump speed may occur over a period of time in an infinitely variable manner instead of a stepwise manner. This gradual ramp-up may occur over a relatively short period of time so that it is not disruptive or perhaps even noticeable by the user, such as a period of about five seconds. This prevents a sudden load on the motor 36 due to the resistance provided by pistons in the air pump 34. At the end of the start-up period, the air pump 34 will be operating at a predetermined operating performance level. This control mode is advantageous for situations such as when substandard voltage levels are available at the job or worksite, or due to lengthy extension cords being used in connection with the air compressor 10. In such situations, a slower ramp-up in speed of the motor output 36 a and of the air pump 34 will prevent the motor 36 from seizing during certain start-up conditions, for example.

While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in some detail, it is not the intention of the Applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The various features of the invention may be used alone or in any combination depending on the needs and preferences of the user. This has been a description of the present invention, along with the preferred methods of practicing the present invention as currently known. However, the invention itself should only be defined by the appended claims. 

What is claimed is:
 1. An air compressor, comprising: an air pump including a pump inlet for receiving air to be pressurized and a pump outlet; an air tank including a tank inlet coupled with the pump outlet for receiving pressurized air from the air pump, and a tank outlet for directing pressurized air from the tank to at least one pneumatic device; a brushless DC motor including a rotatable output coupled with the air pump for operating the air pump to pressurize air; and a control electrically coupled to the brushless DC motor, wherein the control changes the level of electric current drawn by the brushless DC motor between at least a first level and a second, different level to thereby change the rate of rotation of the rotatable output and/or the pump performance level.
 2. The air compressor of claim 1, further comprising an electric power supply coupled to the brushless DC motor and the control.
 3. The air compressor of claim 2, wherein the electric power supply further comprises a DC power supply.
 4. The air compressor of claim 1, wherein the DC power supply further comprises a battery.
 5. The air compressor of claim 4, wherein the control detects the battery as the electric power supply and, in response, causes a predetermined level of electric current to be drawn by the brushless DC motor from the battery.
 6. The air compressor of claim 1, wherein the control further comprises an adjustment device operable by a user to change the level of electric current drawn by the brushless DC motor to thereby change the rate of rotation of the rotatable output and/or the air pump performance level.
 7. The air compressor of claim 6, wherein the adjustment device is operable to allow the user to select between an AC power supply and a battery as an electric power supply coupled to the brushless DC motor.
 8. The air compressor of claim 1, wherein the control further comprises a mode, wherein upon activation of the brushless DC motor, the control gradually increases the level of electric current drawn by the brushless DC motor to thereby gradually increase the rate of rotation of the rotatable output and/or gradually increase the air pump performance level.
 9. The air compressor of claim 8, wherein the control increases the level of electric current drawn by the brushless DC motor to a level corresponding to an operating performance level of the air pump.
 10. A method of operating an air compressor including an air pump operated by a brushless DC motor to fill a tank with pressurized air, the method comprising: supplying electric current to the brushless DC motor to rotate an output of the brushless DC motor; operating the air pump with the rotatable output of the brushless DC motor; directing pressurized air into the tank from the air pump; and changing the level of electric current drawn by the brushless DC motor using an adjustable electric current control coupled to the brushless DC motor to thereby change the rate of rotation of the rotatable output and/or the pump performance level.
 11. The method of claim 10, wherein supplying the electric current further comprises supplying the electric current from a DC power supply.
 12. The method of claim 11, wherein the DC power supply further comprises a battery.
 13. The method of claim 12, further comprising: detecting the battery as the electric power supply; and adjusting the level of electric current drawn by the brushless DC motor to a predetermined level of electric current.
 14. The method of claim 10, wherein changing the level of electric current drawn by the brushless DC motor further comprises using an adjustment device operable by a user.
 15. The method of claim 14, further comprising: using the adjustment device to select between an AC power supply and a battery as an electric power supply coupled to the brushless DC motor.
 16. The method of claim 10, wherein supplying electric current to the brushless DC motor further includes initiating a mode, comprising: gradually increasing the level of electric current drawn by the brushless DC motor upon activation of the brushless DC motor to thereby gradually increase the rate of rotation of the rotatable output and/or gradually increase the air pump performance level.
 17. The method of claim 16, further comprising: increasing the level of electric current drawn by the brushless DC motor to a level corresponding to an operating performance level of the air pump. 